Its both a problem of the cold and the car. You are most likely charging slowly because the battery is cold, I wish the car would tell you why its not charging at full speed (cold limited or station limited). Even if the battery is warm enough you will still never get a full 50kW out of a 50kW charging station, they are rated at 125A@400V and the Kona doesn't have a full 400V pack so you will max out around 46kW I think on a 50kW charger.